I've never understood why an eruption is described as an "explosion." Or why nuclear weapons tests are compared to eruptions in terms of energy released.

Good question.

Volcanic eruptions are just magma geysers of varying viscosity.

They don't normally release their entire eruption power in a single supersonic shockwave like a bomb. I think reporters get excited when they see giant eruption clouds and blown-down forests, and don't consider the mechanisms by which these things actually happen.

Whiskey Dickens:I've never understood why an eruption is described as an "explosion."

Mt. St. Helens would like a word with you. :)

Seriously, though, from what I've seen it would seem that most eruptions involve at least some explosions during the process. Pyroclastic clouds are certainly foreceful enough to merit the term, I would think.

I guess while a volcanic eruption isn't necessarily an explosion, a volcanic explosion is most definitely a form of eruption.

REferring to these events as "explosions" might sometimes be a bit of hyperbole, but really it's not too far form the truth in describing the violent forces typical in volcanic activity.

Whiskey Dickens:I've never understood why an eruption is described as an "explosion." Or why nuclear weapons tests are compared to eruptions in terms of energy released.Isn't it an "explosion" in the same sense that toothpaste "explodes" onto my toothbrush?Always thought an explosion was a really quick exothermic chemical reaction. Not piping hot mag-ma (pinky to mouth) being squeezed through the crust.

Geologist farkers?

IANAG(eologist)

But I'm pretty sure the explody part generally refers to the initial eruption, where pressure has built and is let forth in an explosive manner. Think about the side blowing off Mt St Helens. Or whatever.

"Hey, I'm a civilian. I'm not your lawyer anymore. I'm not anybody's lawyer. I'm just another douchebag with three pairs of Dockers and a job. If I'm lucky, in three months, I'm managing a Cinnabon in Omaha."